What is a Matrix Diagram?
Quality Glossary Definition: Matrix
Also called: matrix, matrix chart
A matrix diagram is defined as a new management planning tool used for analyzing and displaying the relationship between data sets. The matrix diagram shows the relationship between two, three, or four groups of information. It also can give information about the relationship, such as its strength, of the roles played by various individuals or measurements.
Six differently shaped matrices are possible: L, T, Y, X, C, and roofshaped, depending on how many groups must be compared.
When to Use Each Matrix Diagram Shape
Table 1 summarizes when to use each type of matrix. Click on the links below to see an example of each type. In the examples, matrix axes have been shaded to emphasize the letter that gives each matrix its name.
 An Lshaped matrix relates two groups of items to each other (or one group to itself).
 A Tshaped matrix relates three groups of items: groups B and C are each related to A; groups B and C are not related to each other.
 A Yshaped matrix relates three groups of items: each group is related to the other two in a circular fashion.
 A Cshaped matrix relates three groups of items all together simultaneously, in 3D.
 An Xshaped matrix relates four groups of items: each group is related to two others in a circular fashion.
 A roofshaped matrix relates one group of items to itself; it is usually used along with an L or Tshaped matrix.
Table 1: When to use differentlyshaped matrices
Lshaped 
2 groups 
A B (or A A) 
Tshaped 
3 groups 
B A C but not B C 
Yshaped 
3 groups 
A B C A 
Cshaped 
3 groups 
All three simultaneously (3D) 
Xshaped 
4 groups 
A B C D A but not A C or B D 
Roofshaped 
1 group 
A A when also A B in L or T 
LShaped Matrix Diagram
This Lshaped matrix summarizes customers’ requirements. The team placed numbers in the boxes to show numerical specifications and used check marks to show choice of packaging. The Lshaped matrix actually forms an upsidedown L. This is the most basic and most common matrix format.
Customer Requirements

Customer
D 
Customer
M 
Customer
R 
Customer
T 
Purity %

> 99.2

> 99.2

> 99.4

> 99.0

Trace metals (ppm)

< 5

—

< 10

< 25

Water (ppm)

< 10

< 5

< 10

—

Viscosity (cp)

2035

2030

1050

1535

Color

< 10

< 10

< 15

< 10

Drum





Truck




Railcar 



TShaped Matrix Diagram
This Tshaped matrix relates product models (group A) to their manufacturing locations (group B) and to their customers (group C).
Examining the matrix (below) in different ways reveals different information. For example, focusing on model A shows that it is produced in large volume at the Texas plant and in small volume at the Alabama plant. Time Inc. is the major customer for model A, while Arlo Co. buys a small amount. Focusing on the customer rows shows that only one customer, Arlo Co., buys all four models. Zig Corp. buys just one. Time Inc. makes large purchases of A and D, while Lyle Co. is a relatively minor customer.
Products—Manufacturing Locations—Customers
YShaped Matrix Diagram
This Yshaped matrix shows the relationships between customer requirements, internal process metrics, and the departments involved. Symbols show the strength of the relationships: primary relationships, such as the manufacturing department’s responsibility for production capacity; secondary relationships, such as the link between product availability and inventory levels; minor relationships, such as the distribution department’s responsibility for order lead time; and no relationship, such as between the purchasing department and ontime delivery.
Responsibilities for Performance to Customer Requirements
CShaped Matrix Diagram
Because this matrix is threedimensional, it is difficult to draw and infrequently used. If it is important to compare three groups simultaneously, consider using a threedimensional model or computer software that can provide a clear visual image.
XShaped Matrix Diagram
This figure extends the Tshaped matrix example into an Xshaped matrix by including the relationships of freight lines with the manufacturing sites they serve and the customers who use them. Each axis of the matrix is related to the two adjacent ones, but not to the one across. Thus, the product models are related to the plant sites and to the customers, but not to the freight lines.
Manufacturing Sites—Products—Customers—Freight Lines
RoofShaped Matrix Diagram
The roofshaped matrix is used with an L or Tshaped matrix to show one group of items relating to itself. It is most commonly used with a House of Quality, where it forms the “roof” of the “house.” In the figure below, the customer requirements are related to one another. For example, a strong relationship links color and trace metals, while viscosity is unrelated to any of the other requirements.
Frequently Used Matrix Diagram Symbols
Adapted from The Quality Toolbox, Second Edition, ASQ Quality Press.